The present invention relates to the preparation of guanidinium 5,5'-azotetrazolate (GZT).
Various sodium azide (NaN.sub.3) based materials are known for generating gas on combustion. However, there are some problems in using sodium azide, such as high toxicity and high water-solubility. Therefore, much effort has been concentrated on the development of the non-NaN.sub.3 gas generating compounds.
Germany patent No. 4,034,645 disclosed a gas generating compound, guanidinium 5,5'-azotetrazolate, molecular formula C.sub.4 H.sub.12 N.sub.16, molecular weight 284.5, with a very high nitrogen content up to 78.8%. Guanidinium 5,5'-azotetrazolate is a very stable salt and insoluble in common organic solvents except for methanol, DMF, and DMSO. It is sparingly soluble in water and exhibits high thermal stability, as can be seen from its high melting point of 238.degree.-239.degree. C. The particular advantage for the application of this compound is that the generated gas and reaction by-products of combustion are harmless to human beings. This is particularly important when it is used in a closed space.
The manufacturing process described in the Germany patent No. 4,034,645 includes first dissolving 5-aminotetrazole monohydrate in 15% aqueous NaOH solution, then adding powdered KMnO.sub.4 to form sodium 5,5'-azotetrazolate pentahydrate as an intermediate in 51% yield, and followed by reacting with guanidine nitrate to form the final product in 84% yield.